Nonresonant multiphoton ionization of xenon atoms by femtosecond laser pulses

We experimentally study multiphoton ionization of xenon atoms by 266 nm, 400 nm and 800 nm femtosecond laser pulses. The measurements of photoelectron kinetic energy and photoelectron angular distribution indicate that nonresonant multiphoton ionization occurs in the present experimental condition. It obeys the dipolar selection rule and the angular momentum changes one quantum number for adjacent above-threshold ionization peaks.